Diabetes mellitus, a disease characterized by continuous hyperglycemia, is a disorder that affects the metabolization of carbohydrates and lipids. It is a disease aggravated by bloodstream disorders caused by hyperglycemia and systemic complications caused by decreased utilization of sugar. Diabetes mellitus is induced by insulin deficiency or insulin resistance, and diabetes mellitus that occurs due to insulin resistance is called type 2 diabetes mellitus.
Type 2 diabetes mellitus is caused by a malfunctioning of insulin in delivering sugar into cells due to the reduction in the number of insulin receptors or defects in the signal transduction system through a receptor, a condition known as insulin resistance. Type 2 diabetes mellitus directly destroys blood vessels due to hyperinsulinemia and aggravates metabolic syndrome.
Many kinds of drugs have been used to treat type 2 diabetes mellitus. However, except for biguanide metformin, drugs are only partly effective in lowering blood sugar and are not sufficient in effectively preventing serious complications such as loss of sight, paralysis, apoplexy, renal failure, peripheral neuropathy, foot ulcer, etc. For example, a sulfonylurea-based drug forces insulin to be secreted from the pancreas to lower blood sugar. The medicinal effects of the sulfonylurea-based drug disappear immediately. Also, the sulfonylurea-based drug induces an abnormal lipid metabolism, thereby resulting in arteriosclerosis, weight gain, and brain damage caused by hypoglycemia. In addition, a glitazone-based drug is used in combination with metformin because it resolves the problem of insulin resistance in adipose tissues but has a side effect of destroying the retinal vessels. For these reasons, use of the glitazone-based drug requires special attention.
Metformin does not induce hypoglycemia, but it overcomes the problem of insulin resistance in adipose tissues, liver tissues and muscle tissues, and it functions to drastically lower blood sugar and decrease the level of glycosylated hemoglobin.
In addition, metformin is known to activate an AMP-activated protein kinase that physiologically controlls carbohydrate and lipid metabolism and is also reported to decrease blood sugar level, improve lipid condition, and normalize menstrual irregularity, ovulation and pregnancy. Moreover, it has been proven that when metformin is used to treat p53 gene-deficient cancer cells, metformin activates an AMPK enzyme of the cancer cells and changes the metabolic energy pathway, and therefore, the cancer cells finally die [Monica Buzzai et al., Systemic Treatment with the Antidiabetic drug Metformin Selectively Impairs p53-Deficient Tumor Cell Growth, Cancer Res 2007; 67:(14)] since they cannot adjust to the changed metabolic pathway,
In addition, Josie M M Evans reported a study concluding that a type 2 diabetes mellitus patient administered with metformin has a lower risk of cancer than a patient who has not been administered with metformin [Josie M M, Evans et al. BMJ. 2005, 330, 1304-1305]. Moreover, Samantha L. Browker reported that patients with type 2 diabetes mellitus who take metformin orally have a lower cancer mortality rate than patients who take sulfonylurea orally or are administered with insulin [Samantha L et al., Diabetes mellitus Care. 2006, 29, 254-258].
There is an increasing amount of clinical evidence indicating that a cancer stem cell is involved in the recurrence and metastasis of cancer. The content of cancer stem cells in a tumor tissue is 0.2% or less, but the cancer stem cells may not be removed by conventional anticancer chemotherapy. Metformin has an anticancer effect on cancer stem cells and excellent tolerability. In recent research relating to metformin, it has been reported that when doxorubicin, which is an anticancer drug, is administered alone, there is little change in cancer stem cells, but when administered together with metformin, it removes cancer stem cells [Heather A. Hirsch et al., Metformin Selectively Targets Cancer Stem Cells, and Acts Together with Chemotherapy to Block Tumor Growth and Prolong Remission, Cancer Res 2009; 69: (19) Oct. 1, 2009].
However, metformin is generally administered three times a day, and a single dose is approximately 500 mg or more. Thus, to prepare metformin as a sustained-released tablet to be administered once a day, the tablet should contain approximately 1,500 mg or more of metformin, but such a tablet is too large for most patients to take. In addition, since extended release formulation available in the current market contains only approximately 750 mg of metformin, at least two tablets should be taken. For these reasons, a metformin-based substance exhibiting better pharmacological action than conventional metformin and having improved physiochemical characteristics is needed.